The present invention relates to ligno-cellulosic composite panels containing fire retardant solid particle additives, the panels being useful in the commercial and residential building industry. In particular, recycled solid surface sanding dust removed during the finishing of synthetic particle filled resins is employed as the fire retardant additive to economically produce the fire retardant composite wood panel.
Polymeric composite materials made from synthetic polyester, plastic or acrylic resins are commonly used for various applications in the building, electrical and transportation industry. In the interest of safety, such synthetic materials have to fulfill strict flame retardation requirements arising from mandatory government regulations and industry-wide specifications.
Presently, compliance with flame retardation requirements is achieved by incorporating an array of fire retardant additives within the polymeric composites. For example, a common fire retardant, such as alumina trihydrate can be added to a liquid polyester resin or acrylic resin to form a synthetic marble or granite material commonly used in the building industry. The final synthetic granite product is a fire safe, man-made stone with a smooth, polished surface appearance.
Typically, the surface of such fire resistant particle filled resins is polished or smoothed by fine sanding and buffing of the composite surface. The by-product of this process is a very fine particle size sanding dust. Generally, the sanding dust cannot be re-used in the synthetic matrix because the small particle size of the dust will undesirably increase the viscosity of the synthetic matrix material. As a result, the typical practice is to dispose of this sanding dust in landfills. However, this by-product, fine particle size, sanding dust has excellent fire retardant properties due to the high content of fire retardant additives in the original composite, such as alumina trihydrate. Accordingly, there is a need in the industry to effectively recycle and utilize these by-product materials.
In the past, the forest product industry has continued to seek and develop cost-effective fire retardant chemicals for use in ligno-cellulosic composite materials, such as particleboard, fiberboard, oriented strand boards, agricultural straw board and gypsum boards. Typically, fire retardant requirements are achieved by manufacturing and incorporating many types of fire retardant materials in the ligno-cellulosic composite. Although numerous processes for the fire retarding of ligno-cellulosic materials exist, there is always a need for a more cost-effective, environmentally beneficial means to satisfy flame retardant specifications, while maintaining the quality and strength of the ligno-cellulosic materials.
In summary, the present invention relates to a fire retardant ligno-cellulosic panel comprising a mixture of (i) ligno-cellulosic material, (ii) at least one polymeric binder resin, and (iii) fire retardant solid particles comprising fire retardant inorganic materials and a synthetic polymeric material, wherein the mixture is consolidated under heat and pressure to form the panel. Preferably, the fire retardant solid particles are recycled surface sanding dust produced as a by-product during the sanding and buffing of the surfaces of synthetic particle filled polyester, plastic or acrylic resin materials, such as artificial stone, granite or marble composites.
A feature of the invention disclosed herein is to provide a ligno-cellulosic composite material which achieves a Class B fire rating (25 less than flame spread reading less than 75) in accordance with ASTM E-84, while maintaining acceptable strength properties. It is a further object of this invention to utilize a fire retardant by-product material, such as waste solid surface sanding dust, as an effective fire retardant additive for ligno-cellulosic composite materials.